What is the greatest cover version of all time? Jimi Hendrix's blazing version of 'All Along The Watchtower'? Rachid Taha's 'Rock el Casbah'? Richie Havens balearic version of 'Goin Back To My Roots'? OMM, in association with Audi TT Remastered, have picked the 50 greatest covers ever. See if you agree...